Split gate memory device and method of fabricating the same

ABSTRACT

The present disclosure, in some embodiments, relates to a method of forming a memory cell. The method may be performed by forming a sacrificial spacer over a substrate and forming a select gate along a side of the sacrificial spacer. An inter-gate dielectric is formed over the select gate and the sacrificial spacer. A memory gate layer is formed over the inter-gate dielectric and the sacrificial spacer. The memory gate layer is laterally separated from the sacrificial spacer by the select gate. The memory gate layer is etched to define a memory gate having a topmost point below a top of the sacrificial spacer.

REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.16/166,603, filed on Oct. 22, 2018, which is a Divisional of U.S.application Ser. No. 15/332,115, filed on Oct. 24, 2016 (now U.S. Pat.No. 10,147,794, issued on Dec. 4, 2018), which is a Continuation of U.S.application Ser. No. 14/182,952, filed on Feb. 18, 2014 (now U.S. Pat.No. 9,484,351, issued on Nov. 1, 2016). The contents of theabove-referenced patent applications are hereby incorporated byreference in their entirety.

BACKGROUND

Flash memory is an electronic non-volatile computer storage medium thatcan be electrically erased and reprogrammed. Flash cells are used in awide variety of commercial and military electronic devices andequipment. In flash memory cells, over erase associated with stackedgate structures is eliminated by the use of a split gate structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of a pair of adjacent memory cellsaccording to some embodiments of the present disclosure.

FIG. 2 shows a flow diagram of a method according to some embodiments ofthe present disclosure.

FIG. 3 shows a flow diagram of a method for forming split gate memorydevice according to some embodiments of the present disclosure.

FIGS. 4-17 show cross-sectional views at various stages of forming asplit gate memory cell according to some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The description herein is made with reference to the drawings, whereinlike reference numerals are generally utilized to refer to like elementsthroughout, and wherein the various structures are not necessarily drawnto scale. In the following description, for purposes of explanation,numerous specific details are set forth in order to facilitateunderstanding. It may be evident, however, to one of ordinary skill inthe art, that one or more aspects described herein may be practiced witha lesser degree of these specific details. In other instances, knownstructures and devices are shown in block diagram form to facilitateunderstanding.

Split gate memory cells have promising advantages over stacked gatememory cells such as low power consumption, high injection efficiency,less susceptibility to short channel effects, and over erase immunity.The built in select gate transistor in a split gate memory cell caneffectively get rid of the on-chip erase procedures that were used intraditional stacked gate cells to resolve over erase problems.Traditional fabrication methods of the split gate memory cells involvemany processing steps which include patterned masking and dry etchingsteps. The large number of processing steps results in substantialfabrication costs.

Accordingly, the present disclosure relates to a method for creatingsplit gate flash memory cells with fewer process steps than traditionalbaseline processes. Apart from reducing the effective processing cost,this method provides symmetric word gate pairs that are formed around asacrificial spacer. The sacrificial spacer material used in thesacrificial spacer is chosen such that it is compatible with theunderlying silicon substrate as well as the processing steps thatfollow. The method focuses on forming self-aligned gate structures (gatematerial deposited over a sacrificial spacer followed by wet etchingwith no mask involved) and it leads to an easily distinguishable selectgate (SG) feature, where the SG structure will have a non-planar topsurface unlike traditional SG structures.

Some traditional split-gate memory processing techniques include asource side protected masked lithography step for removing word-line(WL) poly from a drain side of the memory cell. This is done in order toisolate neighboring memory cells as well as to reduce contactresistance. The present disclosure does not involve such a step andhence causes less damage to the silicon substrate. Here, after formationof the gate structures, the sacrificial spacer material is easilyremoved, which separates neighboring memory cell pairs as well ascreates an open space for contact formation. Thus, the presentdisclosure presents a cost effective and simple method for fabricatingsplit gate memory cells with self-aligned gate structures.

FIG. 1 illustrates a cross-sectional view 100 of a pair of adjacentmemory cells, according to some embodiments of the present disclosure,namely a first memory cell 101 a and a second memory cell 101 b. Thesememory cells 101 a and 101 b have a first shared common source/drain(S/D) region 104 in a semiconductor body 102 and a first contact 124that connects to the first shared S/D region 104. In some embodiments,the semiconductor body 102 comprises silicon (Si) and the first contact124 comprises Ti/TiN (titanium/titanium nitride) and W (tungsten). Thepair of adjacent memory cells comprises a first gate structure 103 and asecond gate structure 105 that are mirror images of one another. Hence,it is duly specified that all the features illustrated for the firstgate structure 103 are applicable to the second gate structure 105. Thefirst gate structure 103 comprises a first select gate (SG) 106 and afirst memory gate (MG) 110. In some embodiments, the SG 106 and the MG110 comprise poly silicon.

The first MG 110 and first SG 106 have non-planar top surfaces, 113 and115 respectively. Relative to an upper surface of the semiconductorbody, each of these non-planar top surfaces 113 and 115 continuouslyand/or monotonically decrease in height, as one moves along the X-axis,from example, in the direction away from the first contact 124.

In the illustrated example, these non-planar top surfaces 113 and 115are rounded surfaces with different curvatures. The different curvaturesof these surfaces 113, 115 are due to the process steps used to formthem. In the illustrated embodiment, the non-planar SG top surface 115has a first curvature 125, and the non-planar MG top surface 113 has asecond curvature 126 that is non-continuous with the first curvature125. In some embodiments, the curvatures 125 and 126 can be approximatedby different radii, wherein the radius of curvature 125 is greater thanthe radius of curvature 126. Although these curvatures can beapproximately by different radii, it will be appreciated that thecurvatures need not be truly circular, but can be elliptical, parabolic,hyperbolic, and/or have other curvatures.

In some embodiments, each SG of the memory cells 101 a and 101 bcomprises a first select gate side wall 128 a and second select gateside wall 128 b, wherein a height of the first select gate side wall 128a is greater than a height of the second select gate side wall 128 b.Similarly each MG 110 of the memory cells 101 a and 101 b comprises afirst memory gate side wall 128 c and a second memory gate side wall 128d. The first memory gate side wall 128 c, which neighbors the secondselect gate sidewall 128 b, has a height greater than a height of thesecond select gate side wall 128 b. In some embodiments, the height ofthe first memory gate side wall 128 c is also greater than a height ofthe second memory gate sidewall 128 d. Formation of the symmetricself-aligned gates with non-planar top surfaces reduce processing steps(as it involves no mask patterning and CMP processes) thereby reducingthe manufacturing cost. Further, they provide a distinguishable selectgate SG feature that is different from traditional SG structures.

An inter-gate dielectric layer 108 resides in between the first SG 106and the first MG 110. The inter gate dielectric layer 108 furtherextends under the first MG 110. In some embodiments, the inter gatedielectric layer 108 comprises an oxide layer 108 a, a nitride layer 108b, and a second oxide layer 108 c, which are referred to collectively asan ONO (oxide/oxynitride/oxide) structure.

A first dielectric 111 is disposed above the inter-gate dielectric layer108 and is arranged between the neighboring sidewalls of the first MG110 and the first SG 106 to provide isolation between the first MG 110and the first SG 106. In some embodiments, the first dielectric layer111 comprises SiN (silicon nitride). An oxide 112 is deposited along theside walls of the first MG 110 and the first SG 106. Salicide 116 isdeposited over the top surfaces of the SG 106 and the MG 110 as well ason either side of the gate structures 103 and 105 above thesemiconductor body 102. A spacer layer 114 is arranged above both thefirst memory gate 110 and the first SG 106 and has a profile thatfollows the non-planar top surfaces of the first MG 110 and first SG106. In some embodiments, the spacer layer 114 comprises SiN or oxide. Acontact etch stop layer (CESL) 118 is deposited along the oxide 112 andabove the silicide 116. In some embodiments, the CESL layer 118comprises SiN. A dielectric layer 122 is deposited entirely over thesemiconductor body for filling the gaps between the gate structures. Thedielectric layer 122 comprises a BPTEOS(borophosphosilicatetetraethylorthosilicate) layer 120 for gap fillingand a TEOS (tetetraethylorthosilicate) layer 121 above the BPTEOS layer120 for preventing water absorption.

Each memory cell 101 a, 101 b can be thought of as two transistors inseries. One is the memory gate transistor (e.g., corresponding to MG110), and the other is the select gate transistor (e.g. corresponding toSG 106) which is a simple enhancement transistor controlled by the wordline. Programming is performed by means of source-side channelhot-electron injection. Poly-to-poly Fowler-Nordheim (FN) electrontunneling is employed for erasing. To change the cell value to a “0”, anegative electrical potential is applied to both the gates, such thatthe electrons stored in the storage node (ONO layer) are drained to thesource side of the memory cell. The electrons in the cells of a chip canbe returned to normal “1” by the application of a strong positiveelectric field.

FIG. 2 shows a flow diagram of a method 200 according to someembodiments of the present disclosure. While disclosed method 200 (andother methods described herein) is illustrated and described below as aseries of acts or events, it will be appreciated that the illustratedordering of such acts or events are not to be interpreted in a limitingsense. For example, some acts may occur in different orders and/orconcurrently with other acts or events apart from those illustratedand/or described herein. In addition, not all illustrated acts may berequired to implement one or more aspects or embodiments of thedescription herein. Further, one or more of the acts depicted herein maybe carried out in one or more separate acts and/or phases.

At 202 a self-aligned SG is formed abutting a first sidewall of asacrificial spacer. A symmetric SG is formed on a second oppositesidewall of the same sacrificial spacer. The self-alignment creates anon-planar top surface, which leans towards opposite direction on boththe select gates that are formed on either side of the sacrificialspacer.

At 204, a self-aligned memory gate (MG) is formed adjacent the SG.

At 206, an inter-gate dielectric layer is formed in between the SG andthe MG, the inter-gate dielectric layer extending under the MG andleaving a recess between upper regions of the MG and SG.

At 208, the recess left by the inter-gate dielectric layer is filledwith a first dielectric material to provide isolation between the MG andthe SG.

At 210, a spacer layer is formed over the SG and the MG, the spacerlayer following the profile of the SG and the MG and having a non-planartop surface.

FIG. 3 shows a flow diagram of a method 300 for forming a split gatememory device according to some embodiments of the present disclosure.

At 302, a sacrificial spacer material is deposited over a semiconductorsubstrate and patterned with the help of photoresist. In someembodiments, the sacrificial spacer material comprises SiN, SiC and/orSiO2.

At 304, the sacrificial spacer material is etched and the photoresiststripped to create sacrificial spacers over the semiconductor body. Insome embodiments, symmetric sacrificial spacers are formed over thesemiconductor body. In some embodiments the sacrificial spacer materialmay be lithographically defined and removed by either plasma/RIE etch ora selective wet etch.

At 306, a bottom oxide layer is deposited entirely over thesemiconductor body followed by SG material deposition. In someembodiments, the SG comprises poly silicon.

At 308, the SG poly silicon is etched to form SG structures on eitherside of the sacrificial spacers. The etching stops at the bottom oxidelayer.

At 310, an inter-gate dielectric layer is deposited followed bydeposition of MG material. In some embodiments, the inter-gatedielectric layer is the charge storage node and it comprises ONO.

At 312, the MG material/poly silicon is etched to form MG structures oneither side of the sacrificial spacer outside the inter-gate dielectriclayer.

At 314, the first two layers of the inter-gate dielectric layer or theONO layer are wet etched. In some embodiments, the ON (oxy nitride)layer is removed by wet etching.

At 316, a bottom anti-reflective coating (BARC) is deposited entirelyover the ON (oxy nitride) stripped areas.

At 318, the sacrificial spacers are removed or etched off. The oxideabove the sacrificial spacer and the top of the SGs is also removed. Insome embodiments, the sacrificial spacers are removed using a wetetchant combination of HF and H3PO4 (hydrogen fluoride and phosphoricacid).

At 320, a main side wall spacer layer is deposited all over thesemiconductor body and over the gate structures.

At 322, the spacer layer is etched off from the top of the semiconductorbody and from the top of the gate structures, but retained on the gateside walls and over the ONO layer in between the SG and the MG,providing isolation between them.

At 324, a salicide is deposited over the top of the top of the gatestructures and the semiconductor body after removing the oxide fromtheir surfaces.

At 326, a contact etch stop layer (CESL) and interlayer dielectric isdeposited entirely over the semiconductor body covering all the gaps andthey are planarized using a chemical mechanical polishing (CMP) process.In some embodiments, the CESL comprises SiN and the interlayerdielectric layer comprises an oxide.

At 328, another top layer dielectric is deposited over the inter layerdielectric to prevent H₂O absorption and metal contacts are formedextending in to the source/drain (S/D) regions. In some embodiments, theinter-layer dielectric used for filling the gap comprises BPTEOS and thetop layer dielectric comprises TEOS. In some embodiments, the metalcontacts comprises Ti/TiN as a buffer layer which is filled with W.

FIGS. 4-17 show cross-sectional views of a method 300 of forming splitgate memory cells according to some embodiments of the presentdisclosure.

FIG. 4 illustrates a cross-sectional view 400 at one of the stages offorming split gate memory cells according to some embodiments of thepresent disclosure, with patterned photo resist 410 over a semiconductorbody 402. The semiconductor body 402 has S/D regions 404 diffused orformed within. An oxide layer 406 resides on top of the semiconductorbody for protecting the semiconductor body from future etching steps.Over the oxide layer 406 sacrificial spacer material 408 is depositedwhich is subsequently patterned and etched. The photoresist 410 on topof the sacrificial spacer material 408 used is to pattern thesacrificial spacer material to form sacrificial spacers.

FIG. 5 illustrates a cross-sectional view 500 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after the sacrificial spacer material 408 is etchedand the photo resist is stripped off.

FIG. 6 illustrates a cross-sectional view 600 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after depositing or forming an oxide 602 over thesacrificial spacers 408 followed by deposition of the SG poly silicon604.

FIG. 7 illustrates a cross-sectional view 700 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, wherein the SG poly silicon 604 is etched to form SGpairs on either side of the sacrificial spacer 408. In some embodiments,the SG poly silicon is etched off using wet etching without using a maskstep.

FIG. 8 illustrates a cross-sectional view 800 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after depositing an ONO (oxide-oxynitride-oxide)layer and the MG poly silicon 808 entirely over the oxide 406,sacrificial spacers 408 and the SGs 604. The first oxide layer of theONO layer is represented by 802, the nitride layer is represented by 804and the top oxide layer is represented by 806.

FIG. 9 illustrates a cross-sectional view 900 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after etching the MG poly silicon to form MGs 808 oneither side of the sacrificial spacers 408. In some embodiments, the MGpoly silicon is etched off using wet etching which stops at the topoxide layer 806, without using a mask step.

FIG. 10 illustrates a cross-sectional view 1000 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after etching the top oxide layer 806 and thenitride layer 804 of the ONO layer at specified location. In someembodiment wet etching, dry etching, plasma etching or reactive ionetching (RIE) is performed.

FIG. 11 illustrates a cross-sectional view 1100 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, wherein a BARC layer 1102 is deposited at the oxideand nitride stripped areas. This layer protects the underlying layers infuture etching steps.

FIG. 12 illustrates a cross-sectional view 1200 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after removing the sacrificial spacers 408 and theoxide residing over the top surfaces of the sacrificial spacers and thegate structures. In some embodiments, the oxide and sacrificial spacersare removed using a wet etchant combination of HF+H3PO4.

FIG. 13 illustrates a cross-sectional view 1300 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after depositing a main side wall spacer layer 1304over the gate structures as well as over the oxide layer 404. Beforedepositing the spacer layer 1304, an oxide layer 1302 is deposited onthe top surfaces of the gate structures. In some embodiments, the spacerlayer comprises oxide+SiN.

FIG. 14 illustrates a cross-sectional image 1400 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, wherein the space layer 1304 is etched off from thetop surface of the gate structures as well as from the oxide layer 406.The spacer layer 1304 is retained on the side walls of the MGs and theSGs as well as over the ONO layer in between the two adjacent SG-MGpairs.

FIG. 15 illustrates a cross-sectional view 1500 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after removing a layer of oxide and depositing asalicide layer 1502. The oxide layer 406 is removed from the top of thesemiconductor body 402 from areas between the gate structures and theoxide 1302 is removed from the non-planar top surfaces of the gatestructures. Salicide layer 1502 is deposited in the above mentionedoxide stripped areas.

FIG. 16 illustrates a cross-sectional view 1600 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after depositing a contact etch stop layer (CESL)1602 and interlayer dielectric 1604 entirely over the semiconductor bodycovering all the gaps. The inter-dielectric 1604 is planarized using achemical mechanical polishing (CMP) process. In some embodiments, theCESL 1602 comprises SiN and the interlayer dielectric layer 1604comprises BPTEOS.

FIG. 17 illustrates a cross-sectional view 1700 of another stage offorming split gate memory cells according to some embodiments of thepresent disclosure, after depositing another top layer dielectric 1702entirely over the inter layer dielectric 1604 to prevent H2O absorption,and forming metal contacts 1704 that extend downward to the source/drain(S/D) regions 404. In some embodiments, the top layer dielectric 1702comprises TEOS and the metal contacts 1704 comprises Ti/TiN as a bufferlayer which is filled with W.

It will be appreciated that while reference is made throughout thisdocument to exemplary structures in discussing aspects of methodologiesdescribed herein that those methodologies are not to be limited by thecorresponding structures presented. Rather, the methodologies (andstructures) are to be considered independent of one another and able tostand alone and be practiced without regard to any of the particularaspects depicted in the Figs. Additionally, layers described herein, canbe formed in any suitable manner, such as with spin on, sputtering,growth and/or deposition techniques, etc.

Also, equivalent alterations and/or modifications may occur to thoseskilled in the art based upon a reading and/or understanding of thespecification and annexed drawings. The disclosure herein includes allsuch modifications and alterations and is generally not intended to belimited thereby. For example, although the figures provided herein, areillustrated and described to have a particular doping type, it will beappreciated that alternative doping types may be utilized as will beappreciated by one of ordinary skill in the art.

In the description, relative terms such as “lower,” “upper,”“horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and“bottom” as well as derivatives thereof (e.g., “horizontally,”“downwardly,” “upwardly,” etc.) should be construed to refer to theorientation as then described or as shown in the drawing underdiscussion. These relative terms are for convenience of description anddo not require that the apparatus be constructed or operated in aparticular orientation.

In addition, while a particular feature or aspect may have beendisclosed with respect to only one of several implementations, suchfeature or aspect may be combined with one or more other features and/oraspects of other implementations as may be desired. Furthermore, to theextent that the terms “includes”, “having”, “has”, “with”, and/orvariants thereof are used herein such terms are intended to be inclusivein meaning—like “comprising.” Also, “exemplary” is merely meant to meanan example, rather than the best. It is also to be appreciated thatfeatures, layers and/or elements depicted herein are illustrated withparticular dimensions and/or orientations relative to one another forpurposes of simplicity and ease of understanding, and that the actualdimensions and/or orientations may differ substantially from thatillustrated herein.

The present disclosure relates to a method for creating split gate flashmemory cells with self-aligned select gate structures and less number ofprocessing steps than traditional baseline processes. The methodprovides symmetric word gate/select gate pairs that are formed around asacrificial spacer. The sacrificial spacer material used in thesacrificial spacer is chosen such that it is compatible with theunderlying silicon substrate as well as the processing steps thatfollow. The method results in an easily distinguishable select gate (SG)feature, i.e., the SG structure will have a non-planar top surface thatcontinuously and/or monotonically decrease in height along a firstdirection, relative to an upper surface of the semiconductor bodysurface unlike traditional select gate structures. The spacer layer thatcovers the select gate also follows the shape of the SG top surface. Adielectric disposed above the inter-gate dielectric layer and arrangedbetween the neighboring sidewalls of the each memory gate and selectgate provides isolation between them.

In some embodiments, the present disclosure relates to a split gatememory device. The split gate memory device comprises a memory gatearranged over a substrate, and a select gate arranged over thesubstrate. An inter-gate dielectric layer is arranged between sidewallsof the memory gate and the select gate that face one another. Theinter-gate dielectric layer extends under the memory gate. A firstdielectric is disposed above the inter-gate dielectric layer and isarranged between the sidewalls of the memory gate and the select gate.

In another embodiment, the present disclosure relates to an integratedchip. The integrated chip comprises a first select gate and a secondselect gate arranged over an upper surface of a substrate. A sharedsource/drain region is arranged within the upper surface of thesubstrate between the first select gate and the second select gate. Afirst memory gate is arranged over the upper surface of the substrate ata location spaced apart from the shared source/drain region by the firstselect gate. The first select gate has a top surface that monotonicallydecreases in height relative to the upper surface of the substrate as adistance to the first memory gate decreases. An inter-gate dielectriclayer is arranged between the first memory gate and the first selectgate. The inter-gate dielectric layer extends under the first memorygate.

In yet another embodiment, the present disclosure relates to anintegrated chip. The integrated chip comprises a first select gate and asecond select gate arranged over a substrate. A source/drain region isarranged within the substrate between the first select gate and thesecond select gate. A first memory gate is arranged over the substrateat a location separated from the source/drain region by a first selectgate. The first select gate has a top surface that increases in heightrelative to an upper surface of the substrate as a lateral distance tothe source/drain region decreases. An inter-gate dielectric layer isarranged between the first memory gate and the first select gate. Theinter-gate dielectric layer extends under the first memory gate.

What is claimed is:
 1. A method of forming a memory cell, comprising:forming a sacrificial spacer over a substrate; forming a select gatealong a side of the sacrificial spacer; forming an inter-gate dielectricover the select gate and the sacrificial spacer; forming a memory gatelayer over the inter-gate dielectric and the sacrificial spacer, whereinthe memory gate layer is laterally separated from the sacrificial spacerby the select gate; and etching the memory gate layer to define a memorygate having a topmost point below a top of the sacrificial spacer. 2.The method of claim 1, further comprising: etching the inter-gatedielectric after defining the memory gate; forming a masking layer alongopposing outermost sidewalls of the memory gate after etching theinter-gate dielectric; and etching the inter-gate dielectric and thesacrificial spacer in areas exposed by the masking layer.
 3. The methodof claim 1, wherein etching the memory gate layer defines the memorygate along a first side of the sacrificial spacer and further defines asecond memory gate along an opposing second side of the sacrificialspacer.
 4. The method of claim 3, wherein the memory gate and the secondmemory gate are substantially symmetric about a vertical line bisectingthe sacrificial spacer.
 5. The method of claim 1, further comprising:performing a first etching process to remove a part of the inter-gatedielectric from directly over the sacrificial spacer; and performing asecond etching process, after the first etching process is completed, toremove a remainder of the inter-gate dielectric from directly over thesacrificial spacer.
 6. The method of claim 5, forming an anti-reflectivecoating over the inter-gate dielectric between the first etching processand the second etching process.
 7. The method of claim 1, furthercomprising: etching the inter-gate dielectric, after defining the memorygate, so as to recess the inter-gate dielectric to have an upper surfacedirectly between the select gate and the memory gate, the upper surfacevertically below the top of the sacrificial spacer.
 8. The method ofclaim 1, further comprising: forming a second sacrificial spacer overthe substrate; and forming a second select gate along a sidewall of thesecond sacrificial spacer, wherein the select gate and the second selectgate are directly between the sacrificial spacer and the secondsacrificial spacer.
 9. A method of forming a memory cell, comprising:forming a sacrificial material over a substrate; forming a select gatealong a side of the sacrificial material; forming a charge storage layerover the select gate; forming a memory gate over the charge storagelayer; performing a first etching process on the charge storage layerafter forming the memory gate; and performing a second etching processon the charge storage layer and the sacrificial material after the firstetching process is completed.
 10. The method of claim 9, furthercomprising: forming a dielectric layer over a part, but not all, of thecharge storage layer after the first etching process is finished. 11.The method of claim 9, further comprising: forming a source regionwithin an upper surface of the substrate, the source region separatedfrom the memory gate by the select gate; and forming a drain regionwithin the upper surface of the substrate, the drain region separatedfrom the select gate by the memory gate.
 12. The method of claim 11,wherein the charge storage layer has a first outer sidewall facing thesource region and a second outer sidewall facing away from the sourceregion after the second etching process is finished, the second outersidewall completely vertically below a bottom surface of the memorygate.
 13. The method of claim 9, further comprising: forming a memorygate layer over the charge storage layer; and etching the memory gatelayer to define the memory gate, wherein etching the memory gate layerrecesses the memory gate layer below a top of the sacrificial material.14. The method of claim 9, further comprising: forming a dielectric overthe select gate and the memory gate after performing the second etchingprocess; and performing a third etching process on the dielectric,wherein the dielectric remains after the third etching process along asidewall of the select gate, along a sidewall of the memory gate, anddirectly over the charge storage layer.
 15. A method of forming a memorycell, comprising: forming a select gate over a substrate; forming acharge storage layer over the select gate; forming a memory gate overthe charge storage layer; forming a dielectric material over a top ofthe charge storage layer, the select gate, and the memory gate; andperforming an etching process that completely removes the dielectricmaterial from over the select gate and the memory gate, wherein afterthe etching process the dielectric material remains directly over thecharge storage layer.
 16. The method of claim 15, further comprising:forming a silicide over the select gate and over the memory gate afterforming the dielectric material.
 17. The method of claim 15, wherein thedielectric material remains after the etching process along a sidewallof the select gate and along a sidewall of the memory gate.
 18. Themethod of claim 15, further comprising: forming a second dielectricmaterial over the dielectric material, the select gate, and the memorygate; forming an inter-level dielectric (ILD) layer over the seconddielectric material; and forming one or more conductive contacts withinthe ILD layer, the one or more conductive contacts extending from a topof the ILD layer to the substrate.
 19. The method of claim 15, whereinthe dielectric material comprises silicon nitride.
 20. The method ofclaim 15, wherein an imaginary horizontal plane that is parallel to anupper surface of the substrate extends along a top of the memory gate;and wherein the dielectric material is directly between the chargestorage layer and the imaginary horizontal plane.